Optimization of powder factor, fragmentation and oversized boulders through subsystem studies in an opencast coal mine

Document Type : Research Paper


1 CSIR-Central Institute of Mining & Fuel Research, Dhanbad, India.

2 Rock Excavation Engineering Department, CSIR-Central Institute of Mining & Fuel Research, Dhanbad, India.



The massive deposit of medium-grained, white-colored sandstone of about 20 m thick, is located immediately above the coal seam in Quarry No. 2, resulted lesser yield due to lower powder factor (m3/kg) and over-sized boulder formations, specifically from the stemming zones at Chotia Opencast Coal Mine of M/s Prakash Industries Limited, which was operating at a depth of about 30 to 40 m with an average bench height of 5.5 m. The criticality of the problem led to the rectification of the blast design parameters through incorporation of pilot holes and pocket charges, decked charges, air-decking, evolution of static energy distributions, and fragment data analysis for establishing optimized design patterns with available machinery. Several test blasts along with on-site testing of explosive quality, rebound hardness tests of overlying strata, and rearrangements of firing patterns through surface delay connections were considered for adopting the best-suitable blast pattern for the mine. Generalized and perceptible inferences were made to apply the results in other mines with similar kinds of problems.


Main Subjects

[1] Da gama, C. Danis & Jimeno, C. L. (1993). Rock fragmentation control for blasting cost minimization and environmental impact abatement. Proc. 4th International Symposium on Rock Fragmentation by Blasting, Vienna, Austria, (ed. H. P. Rossmanith), Technical University of Vienna, 5-8 July, 273-280.
[2] Konya, C. J. (1987). Controlled backbreak with proper borehole timing. Proc. 13th Annual Conference on Explosives and Blasting Technique, International Society of Explosives Engineers (ISEE), Florida, USA, February 1-6, 49-59.
[3] Konya, C. J. and Walter, E. J. (1990). Surface blast design. Prentice Hall Int. Inc., USA, 303.
[4] CIMFR-CIMFR Report of Investigations (2002). Development of innovative models for optimization of blast fragmentation and muck profile applying image analysis technique and subsystems utilization concept in Indian surface coal mining regime (A. K. Chakraborty et al.). Coal S&T Project No. MT/103/2002-03 of the Ministry of Coal, Govt. of India, January, 125.
[5] Nielson, Kai (1983). Optimization of open-pit bench blasting. Proc. 1st International Symposium on rock fragmentation by blasting, Lulea, Sweden, August, 653-664.
[6] Bhandari, S. (1997). Engineering rock blasting operations. A. A. Balkema, Rotterdam, 375.
[7] Jimeno, C. L., Jimeno, E. L. and Carcedo, F. J. A. (1995). Drilling and Blasting of Rock. Geomining Technological Institute of Spain, A. A. Balkema, Rotterdam, ISBN 90 5410 1997, 391.
[8] Pal Roy, P. and Dhar, B. B. (1993). Comparative assessment of ground vibration and fragmentation in three iron ore deposits in India, Proc. 4th International Symposium on Rock Fragmentation by Blasting (Fragblast’4), July 5-8, Vienna, Austria, 287-293.
[9] Pal Roy, Pijush (2005). Rock blasting effects and operations. Oxford and IBH Publishing Company Pvt. Ltd., New Delhi & A. A. Balkema, Rotterdam, The Netherlands, 345.
[10] Singh, M. M. (1991). Field investigations on the effect of structural discontinuities on rock blasting. Unpublished Ph.D. Thesis, IT, Banaras Hindu University, Varanasi, 180.
[11] CSIR-CIMFR Report of Investigations (2013). Scientific study at Chotia opencast mine of M/s Prakash Industries Limited for better fragmentation, reduction of boulder formation and improvement in powder factor. Project No. CNP/3624/2013-14, India, June, 34.
 [12] JKSimBlast: Blast simulation evaluation and management (2006). Soft-Blast Pty. Ltd., QLD, Australia (www.soft-blast.com). resistivity, theory and application.